How do you validate multipart file uploads in Spring MVC?

Combines multipart limits, metadata validation, content inspection, safe storage, and asynchronous malware processing.

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TL;DR

Spring MVC can bind an uploaded part as MultipartFile or Part, and @RequestPart can convert and validate a JSON metadata part. I configure request and part size limits so oversized input is rejected before consuming excessive memory or disk. I check required presence, allowed business file types, and content signatures rather than trusting only the client filename or Content-Type. Storage uses a generated identifier outside any client-controlled path.

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Multipart binding, request parts, size enforcement, filename distrust, content-type limits, and cleanup.

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Overview
An upload is untrusted content plus untrusted metadata; validation starts before application code receives the part.
Spring MVC can bind an uploaded part as MultipartFile or Part, and @RequestPart can convert and validate a JSON metadata part. I configure request and part size limits so oversized input is rejected before consuming excessive memory or disk. I check required presence, allowed business file types, and content signatures rather than trusting only the client filename or Content-Type. Storage uses a generated identifier outside any client-controlled path.
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Details

Trusting the filename or Content-Type.
Reading every upload fully into memory.
Treating successful receipt as safe content.

How do you validate multipart file uploads in Spring MVC?

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